linux-ext4 - Re: [PATCH 0/2] ext4: Fix possible fs corruption due to xattr races

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Date:   Tue, 7 Jun 2022 14:22:36 +0200
From:   Lukas Czerner <lczerner@...hat.com>
To:     Jan Kara <jack@...e.cz>
Cc:     Ted Tso <tytso@....edu>, linux-ext4@...r.kernel.org,
        Ritesh Harjani <ritesh.list@...il.com>
Subject: Re: [PATCH 0/2] ext4: Fix possible fs corruption due to xattr races

On Mon, Jun 06, 2022 at 04:28:45PM +0200, Jan Kara wrote:
> Hello,
> 
> I've tracked down the culprit of the jbd2 assertion Ritesh reported to me. In
> the end it does not have much to do with jbd2 but rather points to a subtle
> race in xattr code between xattr block reuse and xattr block freeing that can
> result in fs corruption during journal replay. See patch 2/2 for more details.
> These patches fix the problem. I have to say I'm not too happy with the special
> mbcache interface I had to add because it just requires too deep knowledge of
> how things work internally to get things right. If you get it wrong, you'll
> have subtle races like above. But I didn't find a more transparent way to
> fix this race. If someone has ideas, suggestions are welcome!
> 
> 								Honza

I haven't give too much thought towards finding a better way to fix the
race, but this seems like ok solution to me.

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Reviewed-by: Lukas Czerner <lczerner@...hat.com>